Portable radio equipment, particularly those capable of interfacing into the telephone system, require various control or functional changes depending on the mode of operation. For example, there are many instances when the audio coming from the radio needs to be of greater strength due to the physical distance of the radio's speaker from the user. If worn on the belt, the audio would be required to be louder than when at the user's ear. Safety is an additional consideration. When using a radio in a dispatch mode, very loud audio may be required to alert a user if the radio is worn away from the ear i.e. on the hip. When the radio is used near the face, these high audio levels would no longer be required and may actually be damaging if in close proximity to the ear. In this instance, it would be desirable for the unit to automatically convert to a low audio condition for telephone interconnect or low audio dispatch.
Many techniques have been employed which work to reduce the audio level in various situations. These include heat detection and proximity detection which most often are unreliable and costly to implement. Other techniques such as those disclosed in U.S. Pat. Nos. 4,845,772 and 5,276,916 are used with "flip" type cellular telephones. The former uses a hook switch to detect when the flip portion of the radio is extended or retracted. The latter controls the audio output depending on the position of the flip assembly. Until now, only cellular telephones or radios which include these types of flip assemblies have used these techniques. Radios without the flip assembly were not configured to include a switch and therefore could not control any the radio's control functions in specialized situations.
Therefore, the need exits to provide a means by which various radio functions such as audio level, DTMF tone level, light brightness, telephone hang-up or mode of operation can be easily switched and/or controlled depending on the user conditions. The apparatus should be easy to use and inexpensive to incorporate into the radio. The device should have little or no moving parts to insure simple operation and avoid maintenance difficulties.